The reforming of hydrocarbons, such as methane or natural gas, to synthesis gas is an endothermic reaction, meaning that the reaction absorbs heat as it proceeds. In some reaction systems a combination of reforming and oxidation is carried out. In general, this combination reaction process is referred to as autothermal reforming. The advantage of including an oxidation step with a reforming step is that heat that is produced during this step can be used to drive the reforming step.
A. M. De Groote et al., in “Synthesis Gas Production from Natural Gas in a Fixed Bed Reactor with Reversed Flow,” The Canadian Journal of Chemical Engineering, Vol. 74, October, 1996, pp. 735-742, discuss the production of synthesis by partial oxidation of natural gas on a Ni-catalyst in a fixed bed reactor with reversed flow. A one dimensional, non-steady state reactor model was used to simulate the process. The simulation projected the production of synthesis gas having a H2/CO ratio of 2.1, with a conversion of methane between 74% and 80%.
UK Patent Application, GB 2 187 751, discloses a process for producing synthesis gas by catalytic endothermic reaction of organic compounds with steam and/or carbon dioxide. The process uses thermal energy recovered from the partial oxidation of hydrocarbon fuels to carbon monoxide and hydrogen.
G. Kolios et al., in “Autothermal Fixed-Bed Reactor Concepts,” Chemical Engineering Science, 55 (2000), 5945-5967, disclose a variety of autothermal fixed-bed reaction systems. Different reactor types are discussed, as well as basic reaction behavior, stability and nonlinear dynamic features.
Timo Kikas et al., in “Hydrogen Production in a Reverse-Flow Autothermal Catalytic Microreactor: From Evidence of Performance Enhancement to Innovative Reactor Design,” Industrial & Engineering Chemistry Research, 42 (25): 6273-6279 Dec. 10, 2003, describe autothermal reverse-flow operation of a microreactor. The microreactor is a planar reverse-flow microreactor that integrates a mixing chamber, a zero-dead-volume rotating valve and a reaction chamber. Heat from the partial oxidation step of the reaction is used to preheat feed gasses by placing the reaction chamber inside the mixing chamber to capture the heat escaping the reaction chamber in a radial outward direction.
B. Glöcker et al., in “Analysis of a Novel Reverse-Flow Reactor Concept for Autothermal Methane Steam Reforming,” Chemical Engineering Science, 58 (2003), 593-601, discuss asymmetric operation of a reverse-flow steam reforming reactor. Heat consumption during the endothermic step of the operation forms a temperature wave with an expansive low-temperature and a compressive high-temperature part. During the exothermic step of the operation an axial distribution of the heat supply is used in order to maintain a favorable temperature profile in the cyclic operation mode.
Yurii Matros and G. Bunimovich, in “Reverse Flow Operation in Fixed Bed Catalytic Reactors,” Catal. Rev.-Sci. Eng., 38(1), 1-68 (1996), discuss various arrangements of reverse flow reactors. In one arrangement, a reactant is added at an intermediate point or points in the system, and the system is particularly suited to selective catalytic reduction of NOx by ammonia.
Although a variety of autothermal reforming operation systems have been proposed in an effort to efficiently capture and reuse heat, additional and further efficient systems are sought. Systems are also sought in which more a desirable CO and CO2 content of the synthesis gas products can be manufactured.